There is nothing simple or easy about an organic turf program, the same can be said for a chemical based turf program. Both require knowledge, training and experience to be successful. An organic program relies heavily on sound cultural practices and building soil health.
As for a single summer application, most organic fertilizers and/or soil amendments are safe to apply. If you are running a chemical program, one app of organic materials will have minimal effect.
The nation that destroys its soil destroys itself.
Franklin D. Roosevelt